A polyurethane foam (PU foam) layer is made of polyurethane system components comprised of an isocyanate component and a polyol component. Water and a catalyst are added into the polyurethane system components so that the water and the isocyanate component are mixed to produce carbon dioxide by which the polyurethane foam layer is foamed. The PU foam layer is applicable for building materials, packaging material, and vibration absorption material, such as mattresses, cushions or insoles.
As shown in FIG. 1, a method of adhering three polyurethane foam layers together to produce mattresses contains steps of: providing a hard polyurethane foam layer 1, an intermediate polyurethane foam layer 2, and a soft polyurethane foam layer 3 (such as a memory foam), and adhering the hard polyurethane foam layer 1, the intermediate polyurethane foam layer 2, and the soft polyurethane foam layer 3 together by using adhesive 4. However, such a method has defects as follows:
1. The adhesive 4 causes environment damage.
2. The multiple polyurethane foam layers cannot be adhered securely by using the adhesive 4.
3. Due to the multiple polyurethane foam layers having different properties, they foam respectively and then are adhered together, thus reducing production efficiency.
4. After foaming the multiple polyurethane foam layers, the adhesive 4 is clad on the multiple polyurethane foam layers, thereby having troublesome production.
5. After foaming the multiple polyurethane foam layers, the adhesive 4 is clad on the multiple polyurethane foam layers so that the multiple polyurethane foam layers adhere together, but such an adhering method will limit production sizes of the multiple polyurethane foam layers.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.